Conventionally, it has been known that mannan whose constituent sugar is mannose is contained abundantly in palm kernel meal, copra meal, guar meal, and soon, and various methods for producing mannose, mannooligosaccharide and mannose polysaccharides through the function of enzymes to these natural materials have been proposed. Further, such feeds supplemented with mannoses have been known to have the effect of excreting bacteria outside the body (the effect of inhibiting colonization of salmonella ) for inhibiting the colonization of harmful bacteria i.e. salmonella in intestine, and various techniques using this effect have been proposed (Poultry Science, 68, p. 1357, 1989).
For instance, it has been reported that a feed which are prepared by degrading materials containing mannan such as guar meal and copra meal and contains mannobiose and mannotriose as major components where mannooligosacchrides mixed with monosaccharides are blended, can improve the quality of egg of layer. It has been reported, in the meantime, that mannooligosaccharides may be useful in preventing colonization of salmonella in intestine of livestock (Japanese Laid-Open Patent Application No. 1995-236429). It has also been reported that a feed blended with mannose, methyl-α-mannoside, mannooligosaccharide, enzyme of mannan prepared from guar gum, locust bean gum or yeast and/or mannoses such as hydrolysate by acid is/are useful in prevention of harmful bacterial infection such as by salmonella (Japanese Laid-Open Patent Application No. 1996-38064). Further, it has been reported that a feed for livestock blended with mannose-based polysaccharide which mainly contains polysaccharide (30-80%) having 40-100 repeating units of mannose, which also contains oligosaccharide (5-30%), is effective in prevention of colonization of salmonella in intestine of livestock (Japanese Laid-Open Patent Application No. 1996-173055). Besides, a feed blended with degraded product into mannooligosaccharide through the function of enzymes to mannan-rich materials such as palm kernel meal and guar meal, a feed containing mannose prepared through the function of enzymes to copra meal, and a method for producing mannose and/or mannooligosccharide using palm kernel meal have been reported (International Application Published under PCT Nos. 95/17103 and 99/08544, and Japanese Laid-Open Patent Application No. 2001-231591).
Various proposals have been made as mentioned above, but the effect of inhibiting colonization of salmonella in intestine of livestock is still so far from satisfactory sufficient in the present situation that additional modification has been desired. For instance, it has been known that though mannose has an effect of inhibiting colonization of salmonella (an effect of eliminating salmonella ), even if mannose is given to livestock as feed, most of it is easily assimilated by intestinal bacteria and so on, as it being a simple sugar, and it may also be assumed that mannose is digested, absorbed, and excreted by the livestock itself. Further, the result of the experiment by the present inventors provide the knowledge that supplement of a probiotic for enhancing immunity of livestock will further increase mannose-degrading activity and cause the most part of mannose given as a measure for fighting against salmonella to be absent. Accordingly, an extremely large amount of mannose should be administered to actually achieve a sufficient effect of inhibiting colonization of salmonella . On the other hand, knowledge was acquired through the agglutination test using yeast that effects of inhibiting colonization of salmonella by mannooligosaccharide and mannose-based polysaccharide whose molecular weights are larger than that of mannobiose are less significant. The present invention was made in view of the current condition. The object of the present invention is to provide a β-1,4-mannobiose-containing composition which can inhibit colonization of salmonella in animal body and effectively excrete salmonella outside the body and the method for producing thereof, a feed additive containing the β-1,4-mannobiose-containing composition, and a feed blended with the β-1,4-mannobiose-containing composition.
As a result of intensive search, the present inventors acquired knowledge that β-1,4-mannobiose can work more effectively than mannose does in inhibiting colonization of salmonella , since β-1,4-mannobiose has a salmonella -recognition ability and it is difficult to be assimilated by intestinal bacteria of livestock, though its salmonella -recognition ability is slightly inferior to that of mannose. Hence, establishing an efficient method for producing a β-1,4-mannobiose-containing composition and finding that the prepared β-1,4-mannobiose-containing composition has β-1,4-mannobiose at high content, the present inventors completed the present invention.